| 摘要 |
A universal serial bus pre-determining circuit for determining whether a universal serial bus is connected to a host or a device includes an input unit, a detection unit, a processing unit, and a switch unit. The input unit is connected to the host or the device. Once the input unit is connected to the host, the detection unit will enable the host, allowing the host to generate and send a synchronous signal to the input unit. Once the input unit is connected to the device, no synchronous signal will be generated. The processing unit determines accurately whether the universal serial bus is connected to the host or the device by judging the synchronous signal.
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